The present invention is directed primarily to a method for hydroprocessing wheat wherein a wheat product free of husk is obtained and wherein substantially all of the starch granules are maintained in an intact, ungelatinized form and the gluten protein is maintained in a dispersible and substantially undenatured state with respect to the doughing function.
A wheat kernel consists of three major components: the endosperm, the germ and the husk. The husk comprises the outer branny layers lying between and including the aleurone and pericarp tissues and envelopes the starchy endosperm (the source of white flour) and the germ. Although the aleurone, a dense layer of protein-rich, non-starchy cells, overlying the body of the starchy endosperm is technically of endospermal origin, it will be considered as part of the husk herein. In terms of the total weight of the wheat kernel, the husk typically comprises about 14.5%, the endosperm about 83% and the germ about 2.5%.
During conventional dry milling, wheat is ground and the husk, including the aleurone layer, and the germ are mechanically removed from the endosperm. The typical yield of white flour from a dry milling process is from 72% to 74% of the total weight of the wheat. This white flour contains some husk and germ fragments. A significant portion of the endosperm is removed with the husk and germ, thereby limiting the yield of white flour. When attempts are made to increase the yield of white flour, the percentage of husk, aleurone and germ in the flour is progressively increased.
The husk is removed during conventional dry milling because it is the primary source of color in flour, is deleterious to the function of the flour in some applications, and, in some circumstances, nutritionally injurious. The germ is removed to prevent rancid odors attending oxidation of the unsaturated fats contained in the germ.
The wheat flour, to be useful in baking leavened products such as breads and cakes, must support doughing function. In very general terms, doughing describes the phenomenon by which a loose mass of flour particles, when admixed with water, becomes a cohesive, resilient body of dough. As mixing is continued, a resiliently extensible matrix is formed which is capable of entrapping and retaining leavening gas bubbles and which forms an expanded structure which will persist through baking.
For several hundreds of years, dry milling was the only process for making flour from wheat. In more recent times, various techniques for wet milling have been tried with limited degrees of success. Methods for milling wheat and other grains using wet processing and milling techniques are illustrated in Bartmann, U.S. Pat. Nos. 1,670,015 and 1,670,016; De Sollano, et al, U.S. Pat. No. 2,930,699; Rakowsky, et al., U.S. Pat. No. 2,358,827; Anderson, "Wet Milling Properties of Grains"; Bench-Scale Study, Cereal Science Today, Vol. 8, No. 6, p. 190 (July 1963): and Radley, "Starch and Its Derivatives", 3rd Ed., Vol. 2, p. 27 (1953).
Wet milling of corn has, in the past, been more successful than the wet milling of wheat. This is primarily true because the gluten protein of the corn is deliberately degraded in the process of wet milling corn to promote the release of and to improve the purity of the corn starch.
Because starch is the primary desired constituent of corn, wet milling of corn by degrading the gluten protein is reasonably efficient and economical. A series of articles entitled "Wet Process Corn Milling" by Bartline appeared in the American Miller describing this process, e.g., see American Miller, August 1940, pp. 40, 41 and 82; September 1940, pp. 46-48 and 58; October 1940, pp. 28 and 30; December 1940, pp. 25-28, 30 and 84 and 85; February 1941, pp. 32-34 and 89; March 1941, pp. 48, 50, 97 and 98; May 1941, pp. 34-46, 104 and 105; June 1941, pp. 38, 40, 98 and 99; August 1941, pp. 40, 42, 81 and 82; October 1941, pp. 46, 47 and 85; November 1941, pp. 32, 33 and 37; and December 1941, pp. 34, 47 and 86.
Other articles showing wet milling of corn and grain sorghum are Watson, et al., "Laboratory Steeping Procedures Used in a Wet Milling Research Program", Cereal Chem., Vol. 28 (1951), pp. 105-108, and Anderson, "A Pilot Plant for Wet Milling", Cereal Science Today (April 1957), pp. 78-80. Illustrative of patents disclosing the wet milling of corn are Lander, U.S. Pat. No. 1,391,065; Sherman, U.S. Pat. No. 1,554,301; Eckers, U.S. Pat. No. 2,556,322; Newkirk, et al., U.S. Pat. No. 2,573,048; Dowie, U.S. Pat. No. 3,029,169; Slotter, et al., U.S. Pat. No. 2,527,585; Burkhardt, U.S. Pat. No. 251,827; and Willford, U.S. Pat. No. 1,061,933.
Although the literature, as discussed above, is replete with descriptions of wet milling techniques for corn and some other grains, there was, until the inventions of Durst and Winters, U.S. Pat. No. 3,788,861, issued Jan. 29, 1974, and Rogers and Gidlow, U.S. Pat. No. 3,851,085, issued Nov. 26, 1974, no economical or efficient means of hydroprocessing wheat to obtain the endosperm free of husk and in the case of Rogers, et al., free of germ too, wherein the starch granules of the endosperm are maintained in an intact, ungelatinized form and the gluten protein of the endosperm is maintained in a dispersible and substantially undenatured state with respect to doughing function.
The Rogers, et al., patent, U.S. Pat. No. 3,851,085, and the Durst, et al., patent, U.S. Pat. No. 3,778,861, are incorporated herein by reference since the present process represents an improvement on these techniques. Also incorporated by reference herein is Rogers and Durst, U.S. Pat. No. 3,832,472, issued Aug. 27, 1974.
The process of this invention is applicable to hydroprocessing of grain generally, including that process disclosed by the Durst, et al., U.S. Pat. No. 3,788,861. In the Durst, et al. process the entire wheat kernel is ground in an aqueous medium at a temperature of not over 104.degree. F. The husk or bran is then separated from the mixture of endosperm and germ, after which some of the water is removed. Prior to grinding, it is preferred that the polyphenol oxidase activity be reduced below nine activity units. The starch granules are maintained in an intact ungelatinized form and the gluten protein is substantially undenatured with respect to doughing function. The cellular structure of the wheat is disrupted and the starch and protein particles exist independently of each other. The pH is not substantially altered in this process.
While the process of this invention is applicable generally to hydroprocessing techniques, it will be described, for purposes of clarity, with regard to application to the preferred hydroprocess of the previously incorporated by reference Rogers and Gidlow patented process. In any such lengthy process as that described in the Rogers and Gidlow U.S. Pat. No. 3,851,085 patent necessarily there are several periods of long hold time in the overall process. Moreover, typically in the Rogers and Gidlow process the hold time involves the presence of wheat at temperatures ranging from 18.degree. C. up to about 45.degree. C. In addition, during certain of the steps described in the Rogers and Gidlow patented process, fairly complex pieces of equipment are utilized. This complex equipment provides a potential opportunity for some of the wheat being treated in the process to become entrapped in certain areas of the equipment not conducive to ready circulation, referred to herein as "dead spots".
Because of the conditions of temperature and the fact that wheat is an ideal substrate for growth of micro-organisms, care must be taken to insure that any wheat entrapped in dead spots within the system does not become an effective nutrient substrate for the growth of undesirable micro-organisms which might contaminate the overall process and, of course, the end product.
While to date no significant problems have occurred with the practice of the Rogers and Gidlow process, a maximum of safety precautions must be taken with food products. This is especially true because dead spots may exist within the overall Rogers and Gidlow process, because wheat flour is a known effective nutrient substrate for micro-organisms, and because conditions of temperature and moisture are right for the growth of micro-organisms in the system. As can well be appreciated, the growth of pathogenic organisms such as Staphylococcus, Clostridium perfringens, Salmonella and Escherichia coli necessitate a complete shutdown of the process, a complete scrapping of the product, a thorough cleaning, and sterilization before any subsequent attempts to run the process could be conducted.
The improved process of the present invention insures that the hydroprocessing system will not be contaminated by pathogenic organisms.
The improved process of this invention allows operation of steeping-type hydroprocess, such as Rogers and Gidlow, at higher steeping pH's, since no need exists for acid deactivation of micro-organisms. Acid and alkali consumption is thereby reduced and gluten functionality is enhanced.